Polyolefins, as a class of materials, have relatively poor adhesion and compatibility with more polar polymeric materials. In most cases, a separate adhesive is required in order to adhere polyolefins to polar substrates like polyesters, polyamides, polyurethanes, and the like. Similarly, a third component compatibilizer typically has to be used to prepare satisfactory melt blends of polyolefins with other more polar thermoplastics. However, significant amounts of compatibilizers are usually required to maintain the intimate blend of the polyolefin and polyurethane.
In North America, approximately 25 million lbs of flexible polyvinyl chloride (f-PVC) goes into thermoformed sheeting for automotive applications, such as instrument and door panels. Such sheeting is grained, and is color matched with other interior components. Sheeting for automotive applications has to meet several end-use requirements. Key end-use requirements include a low gloss value, a high surface scratch/mar resistance, high heat resistance and good cold temperature impact resistance. In addition, the sheeting must have good adhesion to any intermediate polyurethane (PU) foam layer, for example a foam layer used to provide a softening or cushioning effect to an automotive panel.
The polymeric sheets or skins must be of low gloss, or low glare, especially, if the sheet is placed under a window, such as, in the instrument panel (IP), under the front window of an automobile. Moreover, the gloss of the material must remain low over the vehicle life-time. The gloss of a material is typically determined by measuring reflected light at specified angles, and a typical test measurement is done at 60 degrees. The reflection measurements are converted into gloss values, and these values are typically less than, or equal to, 2, for automotive applications. Flexible or plasticized polyvinyl chloride typically has high gloss values. To reduce the gloss of flexible polyvinylchloride, to acceptable levels for automotive applications, a liquid polyurethane top-coating is typically applied.
Thermoplastic polyolefins (TPOs) sheets can also be used in automotive applications. Thermoplastic polyolefin sheets or skins generally have lower gloss values compared to flexible polyvinyl chloride, but are also polyurethane top-coated to primarily enhance the surface scratch/mar characteristics, and with the secondary benefit of lowering the gloss value. New surface graining technologies (for example, micro-graining, imparted from a grained roller surface to the extruded sheet, during an extrusion) are emerging, however, which will allow for consistent gloss control over a wide variety of grain patterns. These new technologies could foreseeably eliminate the need for PU top-coating of polyolefins that have the right amount of scratch/mar resistance to meet the application requirements. Examples of such new technologies are described in U.S. Pat. No. 5,902,854, which is incorporated herein by reference.
Another end-use requirement is that the sheeting (f-PVC or TPO) needs to withstand the upper service temperatures experienced in the auto interiors, especially in the heat of the summer. The current criterion is that the sheeting withstand a temp. of 120° C. oven aging over 500 hours, while maintaining 50 percent of the original elongation (ISO 188/ASTM E 145, Type IIA, 500 hr at 120° C.), without melting, distorting, becoming tacky, or exhibiting other physical changes. Concurrent with this requirement, is the necessity that the sheeting provide good impact properties at low temperatures, such as at −40° C. This property is particular important when such sheeting is used to form seamless airbags (occupant safety during airbag deployment in winter is of paramount importance; no flying debris is the criteria). The glass transition temperature (Tg) of plasticized polyvinyl chloride is typically −20° C. to −30° C., and thus, this polymer has impaired cold temperature impact properties at temperatures lower than its Tg. Thermoplastic polyolefins, however, typically have lower glass transition temperatures, compared to that of polyvinyl chloride, and thus, have better cold temperature impact properties. Thermoplastic polyolefins are typically the material of choice for seamless airbags and other safety devices, which deploy during a vehicular impact, particularly in cold climates.
Thermoplastic polyolefins also have better long-term durability compared to flexible polyvinyl chloride, as shown by little change in rheological and/or mechanical properties upon heat aging at 120° C. At 120° C., polyvinyl chloride typically loses plasticizer, and therefore loses elongation (elasticity), and becomes brittle and prone to cracking.
Thermoplastic olefin (TPO) sheeting is increasingly being used for soft covered instrument panels and door panels. The typical assembly process requires joining together, in a molding process, a thermoformed flexible thermoplastic polyolefin skin and a hard surface substrate, by forming a polyurethane foam between the two layers. The hard surface substrate is typically composed of a thermoplastic polyolefin, an acrylonitrile-butadiene-styrene (ABS) or an acrylonitrile-butadiene-styrene/polycarbonate (ABS/PC) blend. In instrument panel applications, the ABS and ABS/PC substrates are being replaced by hard TPOs, which are usually reinforced with a filler. A polyurethane precursor mixture (a liquid isocyanate, a liquid polyol and catalyst) is injected between the TPO skin and the hard surface, and then reacted to form a foamed, intermediate layer.
Unfortunately, thermoplastic polyolefins, due to their nonpolar nature, generally lack adhesion to polar materials, such as polyurethanes. Thus, a flexible thermoplastic olefin sheet is conventionally surface treated with a primer solution, containing one or more polar compounds, to increase the adhesion to a polyurethane surface. Typical primer solutions contain a chlorinated maleated polyolefin. Such a surface treatment requires a large ventilation area, equipped to handle sheeting through a gravure application; a primer application mechanism, such as a dip tank; and a drying means to flash off the water and other solvent carriers. In addition, the flexible thermoplastic olefin skin must adhere, without voids and other visible defects, to the polyurethane foam. The polyurethane foam should adhere to the thermoplastic polyolefin surface, without delamination at the interface (or adhesive failure). A discontinuous application of a primer solution may lead to the formation of voids between the thermoplastic olefin skin and polyurethane foam in areas that lack the primer. Surface voids are a costly problem for automotive parts manufacturers, since parts that have surface voids cannot be used in an automotive assembly, and are instead scraped.
International Publication No. WO 00/63293 discloses a thermoplastic polyurethane/olefin-graft polymer blend with an optional compatibilizing polymer. The compatibilizing polymer is a modified polyolefin selected from ionomers, or block and graft olefin polymers that have an unsaturated organic compound in the main or side chain.
European Application No. 0347794A1 discloses a thermoplastic compatible blended composition comprising: (A) from 15 to 60 weight percent of a polyolefin, (B) from 30 to 70 weight percent of a thermoplastic polyurethane, and (C) from 10 to 35 weight percent of at least one modified polyolefin defined as a random, block or graft olefin copolymer having in a main or side chain thereof a functional group selected from carboxylic acid, carboxylate ester, carboxylic acid anhydride, carboxylate salts, amide, epoxy, hydroxy, or acyloxy.
U.S. Pat. No. 6,251,982 discloses a compounded rubber composition comprising: (a) a hydrogenated, polydiene diol based polyurethane having a hard segment content of 10% or greater; (b) a non-polar extender oil in an amount from 10 to 400 phr; and/or (c) one or more thermoplastic resin(s) in an amount from 5 to 100 phr.
U.S. Pat. No. 5,578,680 discloses a vibration-absorbing elastomeric composite, which comprises: (A) 10-60% by weight of at least one thermoplastic resin selected from the group consisting of olefinic polymers, ethylene-unsaturated ester copolymers and natural rubber, and (B) 90-40% by weight of a polyurethane resin, prepared by reacting a polyisocyanate with a polyol insitu in melted thermoplastic resin (A). The polyurethane (B) has a nitrogen atom content of at least 3% by weight, and has a solubility parameter which is higher by at least 2.5 than that of said thermoplastic resin and wherein said composite has a Tan δ of at least 1.0 at 20° C.
U.S. Pat. No. 4,883,837 discloses a thermoplastic compatible blended composition comprising from about 15 to about 60 weight percent of a polyolefin, from about 30 to about 70 weight percent of a thermoplastic polyurethane, and from about 10 to about 35 weight percent of at least one modified polyolefin, defined as a random, block or graft olefin copolymer having in a main or side chain thereof a functional group selected from carboxylic acid, carboxylate ester, carboxylic acid anhydride, carboxylate salts, amide, epoxy, hydroxy, and acyloxy.
U.S. Pat. No. 4,198,327 discloses a composition for adhesion to polar materials, and which comprises the following: a) from 99 to 70 parts by weight of a modified crystalline polyolefin having grafted thereto a monomer selected from unsaturated carboxylic acids and their anhydrides, esters, amides imides and metal salts, and where the crystalline polyolefin has a degree of crystallinity, measured by an X-ray analysis, of at least 25 percent, and which contains the grafting monomer in an amount from 0.0001 to 3 percent by weight, based on the total amount of the crystalline polyolefin and the grafting monomer; and b) from 1 to 30 parts by weight of a hydrocarbon elastomer.
U.S. Pat. No. 5,705,565 discloses a thermoplastic polymer blend comprising one or more thermoplastic polymers, and a substantially linear ethylene polymer grafted with at least about 0.01 weight percent of an unsaturated organic compound containing at least one site of ethylenic unsaturation and at least one carbonyl group. The thermoplastic polymer may be selected from polyurethane, polycarbonate, polystyrene, polyester, epoxy, polyamide, a polyolefin containing polar groups, acrylonitrile-butadiene-styrene copolymer, and mixtures thereof.
European Patent Application No. 0657502A1 discloses a thermoplastic composition containing a mixture of (a) a block copolyether ester, a block copolyether amide and/or a polyurethane, (b) a thermoplastic homo-co- or terpolymer that is incompatible with (a), and (c) a compatibilizer. The compatibilizer is chosen according to the nature of component (b). It will have a backbone that is compatible with, and is preferably identical to, component (b) and a reactive group which is compatible or interacts with component (a). The reactive group may be grafted to this backbone using a grafting monomer having at least one alpha- or beta-ethylenically unsaturated carboxylic acids and anhydrides, and derivatives thereof.
U.S. Pat. No. 6,414,081 discloses a compatibilized blend comprising the following: a) a non-polar thermoplastic elastomer comprising a thermoplastic polyolefin homopolymer or copolymer and an olefin rubber which is fully crosslinked or partially crosslinked; and b) a polar thermoplastic polymer selected from thermoplastic polyurethane (TPU), chloro containing polymers, fluoro containing polymers, polyesters, acrylonitrile-butadiene-styrene copolymers, styrene-acrylonitrile copolymers, styrene-maleic anhydride copolymer, polyacetal, polycarbonate, or polyphenylene oxide; and c) a compatibilizer selected from i) a condensation copolymer formed from 10 to 90 weight percent of a functionalized olefin polymer and 90 to 10 weight percent of a polyamide, based on the total weight of functionalized polymer and polyamide, or ii) a blend of a functionalized olefin polymer and a polyamide, or iii) a mixture of (i) and (ii).
U.S. Pat. No. 6,469,099 discloses a blend of a polymeric hydrocarbon and a thermoplastic polyurethane, which is compatibilized with a polymeric hydrocarbon that contains low concentrations of isocyanate reactive group. The compatibilizer can be prepared by reacting a modified polymer having pendant, or incorporated, amine-reactive groups with a hydroxylamine, a diamine, or a polyethermonoamine. The compatibilized blend may further include a non-TPU engineering thermoplastic to form compatible blends of the polymeric hydrocarbon and the non-TPU engineering thermoplastic.
International Publication No. WO 00/63293 discloses a polymer composition comprising a thermoplastic polyurethane, and a first olefin graft polymer, the graft polymer including at least one first graft moiety and at least one second graft moiety, the first graft moiety being a silane moiety that promotes crosslinking of the grafted elastomer in the presence of moisture, the second graft moiety being an unsaturated organic compound, that, prior to grafting, contains at least one ethylenic unsaturation and a polar functionality that promotes compatibilization of the olefin and the thermoplastic urethane.
U.S. Pat. No. 5,902,854 discloses compositions comprising ethylene interpolymers, such as a linear or substantially linear ethylene interpolymer and polydimethylsiloxane. The compositions may further comprise an ethylene homopolymer or interpolymer grafted with maleic anhydride or succinic anhydride groups. The compositions have good abrasion resistance without sacrificing coefficient of friction.
U.S. Pat. No. 4,397,916 discloses a laminated multilayer structure composed of (A) a layer of a graft-modified ethylene resin grafted with an unsaturated carboxylic acid or a functional derivative thereof, and (B) an oxygen- or nitrogen-containing polar resin layer or a metal layer in contact with the layer (A). The layer (A) is characterized, in part, as consisting of (i) 1 to 100% by weight of said graft-modified ethylene resin derived from an ethylene polymer which contains 0 to 15 mole % of at least one alpha-olefin having 3 to 30 carbon atoms as a comonomer and (ii) 99 to 0% by weight of an unmodified ethylene polymer containing 0 to 50 mole % of at least one alpha-olefin having 3 to 30 carbon atoms as a comonomer.
International Publication No. WO 96/27622 discloses a method of producing nucleophilic amine functionalized polyolefins, by reacting a polymer, carrying an electrophilic functional group, with a diamine having amino end-groups, which have different reactivities. The nucleophilic amine functionalized polyolefin has the composition: Polyolefin-X—R1-NHR2, where X is selected from the group of imide, amide, sulphonamide or amine, R1 is a bivalent organic radical, R2 is H or an alkyl group. The nucleophilic amine functionalized polyolefin has use as a compatibilizer, an adhesive, a dyeable material and a dyeable improver.
International Publication No. WO 93/02113 discloses graft polymers containing reactive amine functionality, and which are prepared by: a) providing a thermoplastic polymer containing at least one electrophilic functionality sufficient to react with primary amino groups; and b) melt reacting with a chemical compound comprising a one primary amine and one secondary amine, the secondary amine having reactivity approximately equal to or less than the primary amine. By utilization of the selected diamine containing chemical compounds, crosslink formation is essentially avoided. The use of the graft polymer as modifier and compatibilizer of polymer compositions is described
International Publication No. WO 03/008681 discloses fibers having improved resistance to moisture at elevated temperatures, and which comprise at least two elastic polymers, one polymer heat-settable and the other polymer heat-resistant, the heat-resistant polymer comprising at least a portion of the exterior surface of the fiber. The fibers typically have a bicomponent and/or a biconstituent core/sheath morphology. Typically, the core comprises an elastic thermoplastic urethane, and the sheath comprises a homogeneously branched polyolefin, preferably a homogeneously branched substantially linear ethylene polymer. A fiber component may contain a functionalized polyethylene. (See also WO 03/008680).
Examples of other compositions with functional constituent(s) are disclosed in U.S. Pat. No. 5,623,019; U.S. Pat. No. 6,054,533; U.S. Pat. No. 5,578,680; EP1672046; EP0734419B1; EP0657502A1. Additional functionalized polymers and/or compositions are disclosed in International Publication Nos. WO 99/02603 and U.S. Publication No. 2004/0106744.
There remains a need for low cost polyolefin compositions that can be used to as good adherents to polar substrates, such as substrates formed from polyurethane, polycarbonate and polyamide. There is a further need for such compositions that can be used in over-molding applications, and which provide improved adhesion to polar substrates. Some of these needs and others have been met by the following invention.
There also remains a need for low cost polyolefin compositions that are capable of further comprising polyurethanes and/or comprising low levels, preferably less than 10 weight percent, compatibilizers. It is of further benefit if such compositions can be used as good adherents to polar substrates, such as substrates formed from polyurethane, polycarbonate and polyamide. It is of even further benefit if articles, such as sheets and films, that have high surface energies, and good adhesion properties can be made. There is a further need for low cost compatiblized blends that have improved heat aging performance, and are particularly suited for automotive interior applications that experience elevated temperatures (as high as 120° C.). There is a further need for such compositions that can be used in over-molding applications and provide improved adhesion to polar substrates. Other potentially useful applications include automotive interior applications (thermoformed skins), and which provide one or more of the following properties: a luxurious feel, lower gloss, and improved grain replication required for negative pressure thermoforming processes. Some of these needs and others have been met by the following invention.
There is also a need to develop polyolefin compositions containing a polyurethane component, and which require a minimal amount compatibilizer or other type of stabilization agent to maintain the stability of the polymer phases of the composition, and which have high surface energies and good adhesive properties. Some of these needs and others have been met by the following invention.
There remains a need for improved, low cost polyolefin/polyurethane compositions containing low levels, preferably less than 10 weight percent (based on total weight of composition), compatibilizers, and that can be used to for, articles, such as sheets and films, and which have high surface energies, preferably greater than 30 dyne/cm, and good adhesion properties. There is an additional need for low cost compatiblized compositions that have improved heat aging performance, and are particularly suited for automotive interior applications that experience elevated temperatures (as high as 120° C.). There is a further need for such compositions that can be used in automotive interior applications (thermoformed skins), and which provide one or more of the following properties: a luxurious feel, lower gloss, and improved grain replication required for negative pressure thermoforming processes.
There are additional needs for suitable thermoplastic polyolefin compositions, which can be used to form sheets that do not require a polyurethane top-coating for gloss or scratch control, and which have good adhesion to polyurethane foams. There is also a need to develop a weatherable, low gloss and/or good scratch mar resistance sheet that has good adhesion to PU foams, PU adhesives and coatings. Some of these needs and others have been met by the following invention.